Graphics issue: geometric/triangle overlay on all graphics as well as a black/grey line obscuring inagr

My son has just purchased and downloaded Minecraft onto his Xbox one. As soon as he started the game there was an immediate issue with the graphics. There is a constant overlay of a geometric pattern - it looks like there are tiny triangles covering the image - and they are always there. As well as this issue there is also a large black or grey horizontal area completely obscuring the screen constantly. 

Things we have tried:

We have uninstalled and reinstalled Minecraft. 
We have cleared the cache on the Xbox one.

We have restarted the Xbox one and we have even disconnected the WiFi and reconnected it: nothing is working. 

please help!

 

Thank you.

 

Jemma